Include user payload in runtime app info response

lib/livebook/session.ex

@@ -3010,7 +3010,7 @@ defmodule Livebook.Session do
     {type, _module, _key} = Livebook.Config.identity_provider()
 
     user
-    |> Map.take([:id, :name, :email])
+    |> Map.take([:id, :name, :email, :payload])
     |> Map.put(:source, type)
   end
 

lib/livebook/users/user.ex

@@ -16,6 +16,7 @@ defmodule Livebook.Users.User do
           id: id(),
           name: String.t() | nil,
           email: String.t() | nil,
+          payload: map() | nil,
           hex_color: hex_color()
         }
 

test/livebook/session_test.exs

@@ -1493,7 +1493,8 @@ defmodule Livebook.SessionTest do
                     source: :session,
                     id: "1234",
                     name: "Jake Peralta",
-                    email: "jperalta@example.com"
+                    email: "jperalta@example.com",
+                    payload: nil
                   }
                 }}